The present invention broadly relates to a magnetic disk apparatus having a magnetic disk as a magnetic recording medium and a core slider as a magnetic head which floats above but is held adjacent to the magnetic disk so as to record and reproduce data on and from the recording medium. More particularly, the present invention relates to a structure for supporting the magnetic head in a magnetic disk apparatus of the type specified above and which is improved to increase the recording density and to shorten the access time.
A typical known magnetic head supporting structure is disclosed in Japanese Unexamined Patent Publication No. 55-22296 (corresponding to U.S. Pat. No. 4,167,765) and has a gimbal member 2 (see FIG. 4) which holds a core slider 1 as the magnetic head and a loading beam member 4 to one end of which the gimbal member 2 is secured. The gimbal member 2 is made of a thin resilient plate member to one end of which the core slider 1 is attached. A loading projection 3 is provided on the portion of the gimbal member 2 where the core slider 1 is mounted, in such a manner as to spherically project in the direction opposite to the core slider 1.
As in the case of the gimbal member 2, the loading beam member 4 is made of a thin resilient plate. The other end of the gimbal member 2, i.e., the end of the gimbal member opposite to the core slider 1, is secured to one end of the loading beam member 4. The loading projection 3 of the gimbal member 2 contacts the other end of the gimbal member 2 so that the loading beam member 4 loads the gimbal member 2 through the loading projection 3 so as to urge the core slider 1 towards a surface of a magnetic disk 5 which is a magnetic recording medium. The loading beam member 4 is connected at its other end to a driving means 6. When the driving means 6 is activated to move linearly, the core slider 1 held by the gimbal member 2 is moved in the radial direction of the magnetic disk 5.
According to the described prior art construction of the magnetic head supporting structure, the loading beam member 4 urges, through the loading projection 3, the core slider 1 towards the surface of the magnetic disk 5. During the rotation of the magnetic disk 5, a flow of air is generated by the running surface of the magnetic disk 5 and causes the core slider 1 to be moved away from the surface of the magnetic disk 5 against the urging force produced by the loading beam member 4, while the magnetic disk 5 is scanned by the core slider 1 in the radial direction as a result of the linear movement of the loading beam member 4, whereby data is recorded on a desired portion of the magnetic disk 5 or read from a desired portion of the magnetic disk 5. By virtue of the spherical form of the loading projection 3 which is supported by the loading beam member 4 through the gimbal member 2, the core slider 1 is always oriented to squarely face the plane of the surface of the magnetic disk 5, thereby ensuring a high degree of recording and reading accuracy of the data.
There is a current demand, in order to achieve a higher recording density, to decrease the distance of the core slider from the surface of the magnetic disk. Also, it is desired to increase the seeking speed of the core slider to shorten the access time required for the core slider to access to a desired track on the magnetic disk.
The prior art magnetic head supporting structure described above, however, cannot fully meet these demands because, when the core slider 1 is driven by the loading beam member 4 during seeking, the core slider 1 tends to oscillate in the rolling direction and tilt as illustrated in FIG. 5. This is due to an acceleration generated during the movement, with the result that the core slider 1 abnormally approaches the surface of the magnetic disk 1 or undesirably contacts it.
More specifically, when the core slider 1 moves, the core slider 1 receives a force F which is represented by F=m.multidot..alpha. where m represents the mass of the core slider 1 while .alpha. represents the acceleration. This force F is applied to the gimbal member 2 and is borne at a point P where the gimbal member 2 is secured to the loading beam member 4. In consequence, a moment M=F.times.L, where L represents the distance (l.sub.1 +l.sub.2) between the point P and a centroid O of the core slider, is generated about the point P.
The core slider 1 is spaced from the magnetic disk 5 by an extremely small distance or gap. The moment M tends to cause the core slider 1 to oscillate in the rolling direction about a fulcrum which is constituted by a point Q where the loading projection 3 and the loading beam member 4 contact each other, with the result that a portion of the core slider 1 becomes abnormally close to the magnetic disk 5 or contacts the same.
This problem is serious, particularly when the lift or floating distance of the magnetic head from the disk is decreased for attaining a higher recording density and the seeking speed is increased for the purpose of shortening the access time.